1. Field
At least one feature relates to communication systems, and, more particularly, to a method for resynchronizing an access terminal with a server using a secret key.
2. Background
The field of communications has many applications including, e.g., paging, wireless local loops, Internet telephony, and satellite communication systems. An exemplary application is a cellular telephone system for mobile subscribers. (As used herein, the term “cellular” system encompasses both cellular and personal communications services (PCS) system frequencies.)
In communication systems, a user or access terminal may establish a data connection to communicate with a server for sending and receiving messages, such as Short Message Services (SMS) messages. In order to protect the SMS messages from being attacked, the access terminal and server may protect the SMS messages by various known methods in the art, such an encryption using a key. For example, when the server and access terminal communicate with each other they might share a key so that when the server sends a SMS message to the access terminal it will add a message authentication code tag to the SMS message which is computed using that key. The message authentication code tag on the SMS message allows the access terminal to verify the source of the message. This method of protection works well unless the access terminal loses the key or if the key gets changed in memory causing synchronization to be lost between the access terminal and the server. If the access terminal and server lose synchronization, then the server needs to send a push message to request the client to resynchronize. However, finding a secure way for the server to initiate resynchronization that cannot be exploited by attackers is problematic. Consequently, a secure way for the server to initiate resynchronization with an access terminal that cannot be exploited by attackers is needed.